Custom theme color: support light-dark shades

[Aiuanyu]

Preliminary Checks

• I have read and understood the important section above.
• I have searched existing issues and avoided creating duplicates.
• I am not filing an enhancement request.
• I have checked that this issue cannot be reproduced on Mozilla Firefox.
• I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

Please do not remove the color input field altogether like in 1.14.6b,
because I need to input such CSS syntax by myself, to enable better transparency (I use #titlebar backdrop-filter blur), and more clear light-dark differences, as below:

Expected behavior

Please always leave a custom input field or other interface for such customization, thanks!

Actual behavior

Input field < 1.14.5b is removed.

Steps to reproduce

Open "Edit theme" dialog for each workspace.

Screenshots and videos

No response

Version

1.14.6b

What platform are you seeing the problem on?

macOS - aarch64

What component is this issue related to?

Customizable UI / Toolbars

Relevant log output if applicable

[mr-cheffy]

The same setup can be achieved by just using HEXs, why are you adding color-gradients as colors?

[Aiuanyu]

First of all I'm not typing color-gradients myself. I'm using color-mix:

color-mix(in srgb, rgb(200, 71, 128) 30%, color-mix(in srgb, light-dark(var(--zen-branding-bg), #171717) 50%, transparent 50%) 70%)
color-mix(in srgb, rgb(230, 193, 209) 30%, color-mix(in srgb, light-dark(var(--zen-branding-bg), #171717) 50%, transparent 50%) 70%)
color-mix(in srgb, rgb(179, 222, 234) 30%, color-mix(in srgb, light-dark(var(--zen-branding-bg), #171717) 50%, transparent 50%) 70%)
color-mix(in srgb, rgb(38, 148, 180) 30%, color-mix(in srgb, light-dark(var(--zen-branding-bg), #171717) 50%, transparent 50%) 70%)

Here's what can be achieved here with light-dark switch, and also transparency and translucency:

Comparing with the HEX-only you are working on (no dark shade):

Or can you add a light-dark difference in the new mechanism? Thanks.

(Not a Chinese here, but a Taiwanese by the way, although we use some similar writing system.)

[Aiuanyu]

(Updated my comment with a new screenshot to compare whether light-dark switch is used.
Took translucency out of the request because can be achieved with HEX RGBA value.)